I've had this happen before. You file a complaint with eBay and they will try to get him to pay. If he doesn't then they will put a strike against him. Once he gets three strikes they will block his membership.

"If I could go back in time and like tell 11 year old me that like not only do you get to go to Comic Con but you go every year. So much so that you get greeted by Stan Lee when you show up. And 11 year old me would be like - How did we get so fat?" - Kevin Smith